Tribromindigo and process of making same.



I indigo with bromin.

UNITE ru ns PATENT omnon.

WILHELM BAUER, 0F VQHWINKEL, NEA

a ELBEEFELD, AND ALFRED HERRE, or ELBERFELD, GERMANY, ASSIGNORS TO FARBENFABRIKEN vomvr. FRIEDR. BAYER & 00., or ELBERFELD, GERMANY, A oonronartou 0F GERMANY.

TRIBROMINDIGO AND PROCESS OF MAKING SAME.

N 0 Drawing.

Specification of Letters Patent.

Application filed September 15, 1908. Serial No. 453,163.

Patented Oct. 19, 1909.

and useful lmproven'lcnts in 'lribromoindigo and Processes of Making Same, of which the following is a specification.

Our invention relates to the manufacture and production of a new tribromo substitution product of indigo. It is obtained in a very simple manner and with a very good yield by treating at a moderate temperature in presence of concer rated sulfuric acid The new tribromo derivative of indigo thus obtained is a valuable dyestutl'. It forms vats by the usual methods in use for preparing indigo vats.

These vats dye umnordanted cotton greenish-blue shades remarkable for their elcarness and fastness. I

The new tribromoindigo is distinguished from the tribrominated indigo of thebld art by yielding more greenish shades than the tribrominated indigo of the old art ;t. it is also more soluble in organic solventsand its leuco compound is more soluble in alkalies. It is soluble in hot glacial acetic acid and easily soluble in hot phenol and benzaldehyde with a blue color. By treatment with oxidizing agents our new compound furnishes a product from which a bromoisatin of the melting point of about 215 (1. may be isolated while the product furnished by the oxidation of the tribromoindigo of the old art consists of bromoisatins melting at y about 250 C.

In order vto illustrate the new process more fully the following examples are given, the parts being by. weight.

Example I: 1.0 parts of finely powdered indigo are gradualy introduced while stirrin' into 250 parts of com-entrated sulfuric (C6 86.), which has to be cooled to prevent sultonation of the indigo. 18 parts of bromin are then added in such a manner that its addition takes about halt an hour.

After stirring the mixture tor two hours it is heated to 30" C. and it is then kept. at this temperature for three hours. while the stirring is continued all the time: subsetplently the mixture is poured into water containing a small quantity of bisultite and the new hi i warm water, and dried.

- low bromoindigo which separates isfiltered ofl, treated with a dilute solution of caustic alkali at 80 C., filtered again, washedwith It-is a reddishblue powder, soluble in concentrated sulfuric acid with a greenish-blue color.

lVhen treated with alkaline reducing agents e. g. hydrosulfite and NaOH thenew tribromoindigo yields a yellow vat containing the leuco compound from which unmordanted cotton is dyed in greenish -blue shades, which on being touched with concentrated nitric acid behave very similar to shades produced with indigo, namely a yelspot appears with a greenish circle around it, while tlie shade of the tribromoindigo of the old art turns slowly greenishgray with concentrated nitric acid.

It is not necessary to use in the above example the theoretical amount of bromin because the hydrogen bromid, formed during the reaction, is oxidized by the sulfuric acid, and will supply the bromin necessary for the completion of the reaction. \Ve can,

therefore, carry out our process with a considerably smaller amount of bromin than theoretically 'alculated.

Example II: 10 parts of finely powdered.

indigo are gradually introduced while stirring into 250 parts of concentratedsulfuric acid. (66 156.), which has to be cooled to prevent sulfonation of the indigo. 12 parts of bromin are then added in such a manner that its addition takes about half ali hour.

After stirring the mixture for two hours it is heated to 30 C. and it is then kept at this temperature for three hours, while the stirring is continued all the time. Subsequently the mixture is poured into water containing a small quantity-of bisullite and the new tribrornoindigo which separates is filtered oil", treated with a dilute solution of caustic alkali at (L, filtered again, washed with warm water, and dried.

\Ve have. further found that the bromination ol indigo can also be carried out by using hydrobromic acid -(l lBr) alone, and welound that even ln'on'lid of sodium or other dnromids can be employed directly in the presence of sulfuric acid.

llxample l ll: it? parts oi indigo are introduced into 300 parts oisullurie'acid (66 l6.) cooled to from i 10" (l. below 0 and 'ltl parts of powdered smlium bromid (NaBr) are added at this temperature. The mixture is-stirred for 20 hours, the temperature being allowed to rise in the course of 15 hours to 45 C. It is kept at this temperature for a further 5' hours and is then poured onto ice. The tribromoindigo which separates is filtered off and dried.

The new dye can also be obtained by start ing instead of from indigo, from bromoindigo containing a lower percentage of bromin than the tribromoindigo.

Having now particularly described and ascertained the nature of our invention and inwhat manner the same is ,to be performed, we declare that what we claim is 1. The herein-described process for producing tribromoindigo, which process conabsence of water, substantially as described.

3. The herein-described new tribromoindigo obtainable by treating indigo in the presence of concentrated sul ric acid with romin, which product is a reddish-blue powder, soluble in concentrated sulfuric acid with a greenish-blue color, soluble in hot glacial acetic acid and easily soluble in hot phenol and benzaldehyde with a blue color; furnishing by treatment ,with oxidizing agents a product from which a bromoisatiu melting at 215 C. may be isolated; and yielding b treatment with hydrosulfite and caustic so a lye a yellow vat, from which unmordanted cotton is dyed greenish-blue shades. which turn quickly yellow when touched with concentrated nitric acid, substantially as described.

In testimony whereof we have hereunto set our hands in the presence of two subscribing witnesses.

WILHELM BAUER. p 1 8. ALFRED HERRE. [n.s] 

